Well, the idea is that there is a beneficial impact on the giver. In modern Western terms, it would be the equivalent of thinking that the act of giving to mon

Well, the idea is that there is a beneficial impact on the giver. In modern Western terms, it would be the equivalent of thinking that the act of giving to monks has a positive impact on your self-image and your idea of how to relate to wealth and the community, which is true even if it turns out that, for example, due to an accident of some sort after you leave the food has to be thrown out. Of course, there is usually an assumption that supporting a monk in their holy work also has a beneficial effect, and if they're all meth-addicts that might not be the case, but there is some non-zero benefit to the giver, regardless.